The present invention generally relates to apparatus, systems, and methods by which a target area is adequately illuminated by one or more lighting fixtures, each of which employs a plurality of aimable light sources. More specifically, the present invention relates to improvements in the design and use of modular light-emitting diode (LED) lighting fixtures such that the compact nature of the fixture is not compromised while flexibility in addressing the lighting needs of a particular application (e.g., sports lighting) is increased.
It is well known that to adequately illuminate a target area—particularly a target area of complex shape—a combination of light directing (e.g., aiming, collimating) and light redirecting (e.g., blocking, reflecting) efforts are needed; see, for example, U.S. Pat. No. 7,458,700 incorporated by reference herein. This concept is generally illustrated in FIGS. 1A-C for the example of a sports field illuminated by a plurality of elevated floodlight-type fixtures. As can be seen from FIG. 1A, in the un-aimed state a fixture 4 illuminates some portion of target area 5 (which typically comprises not only the horizontal plane containing the sports field, but also a finite space above and about said field); this illumination is diagrammatically illustrated by composite projected beam 7 (i.e., a composite of individual outputs from plural fixtures 4) wherein the hatched portion of beam 7 is considered desirable. Adjusting fixtures 4 relative to pole 6 (i.e., directing light) aims composite beam 7 toward the leftmost portion of target area 5 as desired (see FIG. 1B) but also results in the lighting of undesired areas such as bleachers 515. This light, commonly referred to as spill light, is wasteful and a potential nuisance (e.g., to spectators in bleachers 515) or hazardous (e.g., to drivers on a road adjacent to target area 5). To adequately eliminate spill light, a visor or analogous device may be added to fixtures 4 (see FIG. 1C) to provide a desired cutoff—i.e., redirect light. Some visors, such as those disclosed in U.S. Pat. No. 7,789,540 incorporated by reference herein, are equipped with inner reflective surfaces so to both cut off light and redirect said light back onto target area 5 so it is not absorbed or otherwise wasted.
This general approach to lighting a target area has worked well for traditional lighting systems employing a single visor for a single, large light source with high, omnidirectional light output (e.g., 1000 watt high-intensity discharge (HID) lamps). More recently, this approach has been applied to a plurality of small lights sources with low, directional light output (e.g., many 1-10 watt LEDs) and found success—but only for some lighting applications.
There is movement in the art towards LEDs lighting for everything from general task lighting to more demanding applications such as wide area lighting. Compared to traditional light sources such as the aforementioned, LEDs have a higher efficacy (lumens/watt), longer life, are more compliant with environmental laws, and have greater options for color selection, to name a few benefits. Further, replacing a single traditional light source with a plurality of compact and aimable light sources provides the potential to create complex beam patterns from a limited number of fixtures since the light output from each LED can be precisely and independently directed and redirected; if, of course, that potential can be logically and economically realized.
While a host of LED lighting fixtures have been designed for downlight applications (i.e., lighting applications that direct light generally downward towards the base of a pole to which the LEDs are affixed)—see, for example, U.S. Pat. Nos. 7,771,087 and 8,342,709—pivot those fixtures about their connection point to a pole so to project light outward and away from the pole (i.e., a floodlighting application such as that illustrated in FIGS. 1A-C) and a problem becomes apparent; namely, glare. Because there is no external visor on LED fixtures such as the aforementioned, the LEDs are directly viewable and cause glare. One might add an external visor such as in FIG. 1C so to reduce glare, but then there is the concern of undesirable lighting effects such as shadowing and uneven illumination because the LEDs contained therein are each aimed and paired with an optic so to produce a fixed aiming angle and beam pattern—and are not designed to cooperate with a single external visor.
Further, when adding an external visor to provide glare control for an outdoor lighting application such as that illustrated in FIGS. 1A-C, one must consider how the visor affects the fixture's effective projected area (EPA). An increased EPA may require a more substantial pole or more robust means of affixing the fixture to the pole so to address increased wind loading, which may add cost. Given that a typical wide area or sports lighting application utilizes multiple poles with many fixtures per pole—see, for example, aforementioned U.S. Pat. No. 7,458,700—the added cost from even a slight change to EPA can be substantial. Thus, attempting to modify an existing LED downlight fixture to produce an LED floodlight fixture which is suitable for a sports lighting application may not be economically feasible.
Accordingly, there is a need in the art for a design of lighting fixture which can realize the benefits of multiple small light sources such as LEDs (e.g., long life, high efficacy, ability to aim to multiple points, greater flexibility in creating lighting uniformity, etc.) while preserving desirable features of a lighting fixture (e.g., low EPA, high coefficient of utilization, suitability for outdoor use, etc.) in a manner that addresses the lighting needs of a demanding application (e.g., wide area, sports lighting, and the like) while avoiding the undesirable lighting effects (e.g., uneven illumination, shadowing effects, glare, etc.) evident when simply modifying existing LED lighting fixtures.